American Urological Association - Atypical Adenomatous Hyperplasia (AAH)
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Atypical Adenomatous Hyperplasia (AAH)

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Image B

  • Also known as adenosis, is a nodular proliferation of closely spaced small benign atypical glands.
  • Occurs mostly in the transition zone (TZ).
  • Usually an incidental finding, seen in up to 19% of TURP, <1% of needle biopsy and 33% of radical prostatectomy.
  • A differential diagnosis for well-differentiated prostate carcinoma in biopsy.
  • Histology:
    • Lobular proliferation of small glands with minimal infiltration into the surrounding stroma (glands architecture overlap with cancer) (image A) & (image B).
    • Abundant cytoplasm, pale to clear.
    • Occasionally, crystalloids, amorphous eosinophilic secretions or mucin can be seen intraluminally (usually you see these features in cancer!).
  • Immunohistochemistry: discontinuous staining for basal cell markers HMWK and p63 (cancer in contrast has complete absence of basal cells).
  • Experts suggest that majority of the original Gleason grade 1 which is rarely diagnosed these days were Atypical Adenomatous Hyperplasia (AAH) (no immunohistochemistry yet at that time to look for basal cells).
  • Weak evidence to suggest that AAH may represent a preneoplastic process, particularly for low-grade prostate carcinoma in TZ.